Looks like there is dependency on nokogiri, which is not listed, also required ruby version is 2.1, so this gem won't work on 2.0 (which is CentOS 7 default)
Also it complains that dns_record.rb, host.rb and email_forward.rb are not found. I had to download those files from https://github.com/yuxir/NamesiloRubyClient/tree/master/lib
is it possible to fix those issues?